DE1667129C3 - Process for removing homogeneously dissolved impurities, in particular oxygen, from gases or liquids - Google Patents

Description

The invention relates to a method for removing homogeneously dissolved oxygen as an admixture, Nitric oxide, hydrogen halide, halogen, hydrogen sulfide, sulfur dioxide, sulfur trioxide, ammonia and / or carbon monoxide from gases, saturated or aromatic hydrocarbons or ethers.

It is often required. Gases or liquids from to free the additions mentioned, for example for the extraction of gases or liquids in pure form, to avoid disturbances caused by the presence of such secondary components odtr for the analytical detection of the added substances.

There are already various measures for the separation of such additions chemically as well as physically known, for example from German patent specification 9 65 634, Angewandte Chemie 70, pages 697 to 699 (1958), Angewandte Chemie 72, pages 132 to 135 (1960) and from "Inorganisch-preparative chemistry" by H. G r u b i t s c h, Vienna, 1950, pages 257 and 258.

However, these known measures have more or less major disadvantages. This is true in special measure for the removal of oxygen. So are some known measures for this purpose cumbersome and time-consuming, and others can only be used in certain cases. It is also sufficient often the extent to which the oxygen is removed does not meet practical needs, especially then not if a relatively small amount of oxygen is to be removed. Occur in many cases even have several of these disadvantages at the same time.

There is therefore the task of removing homogeneously dissolved impurities, in particular Improve oxygen, from gases or liquids

Table I.

and simplify.

A process has now been found for removing homogeneously dissolved oxygen, nitrogen oxide, hydrogen halide, halogen, hydrogen sulfide, sulfur dioxide, sulfur trioxide, ammonia and / or carbon monoxide from gases, saturated or aromatic hydrocarbons or ethers using a mass consisting of a carrier material with one or more applied metal components and which has been treated at elevated temperature with oxygen and / or reducing gases, in which, according to the invention, the admixtures are removed by chemisorption by the gases or liquids with a at 300 to 600 ⁰ C with Tiolekularem Oxygen activated and then treated with a reducing gas at a temperature between 200 ° C to below the respective activation temperature of an active material containing iron, nickel, rhenium, preferably titanium, manganese, vanadium, molybdenum and / or chromium Component on a heat-resistant Nondigen oxidic carrier with a large surface are brought into contact.

Oxygen can be particularly effective when using a mass with a chromium-containing component remove.

A large number of heat-resistant oxidic carriers are known. For the purposes of the invention, for. B. oxides of silicon, aluminum, zirconium and thorium and mixtures thereof are suitable. The surface area of the carrier materials used is preferably 200 to 500 m ² / g. Some examples of such carriers are given in Table I below.

(Protected) Manufacturer Together surface Grit description settlement Marlex Phillips SiO ₂ 77% approx. 400 m ² / g powder petroleum AI2O3 13% Company H2O 10% MS 969 BASF S1O2 aq approx. 300 mVg powder Aerosil Brave S1O2 aq approx. 320 m ² / g powder No. 2491

l'Drlsct / unu 3 1 Manufacturer 667 129 surface 4th Grit (Protected)
description Merck
No. 7733
Schuchardt
No. 51 157
Riedel-De Haen Together
settlement 0.2-0.5 mm
2-5 mm
powder Silica gel
Silica gel
AI2O3 for SiCh ■ aq
S1O2 - aq
(97-98%)
(2-3%)
AI2O3 aq

Chromatography No. 31 154

The ready-to-use compound is produced in 3 stages.

1. Application of the transition metal to the carrier (doping),

2. Activating with oxygen at elevated temperatures and

3. Treatment with reducing gases, also at elevated temperatures.

For applying the active ingredient to the carrier, generally those for such purposes can be used known measures are applied. The carrier is expediently mixed with an aqueous solution impregnated with the desired transition metal compound. The choice of suitable metal compounds is within the skill of the art. Some Examples of such metal compounds which have been applied to the carrier in aqueous solution are further listed in Table II, Column 2 below. The wäB.ige Solution is preferably used in such an amount and concentration that the impregnated air-dry Carrier the metal component in an amount of 1 to 5 wt .-%, based on the metal content, contains, but smaller or larger amounts can also be used.

Then the mass is dried and activated with molecular oxygen at elevated temperatures. To do this, a stream of pure oxygen or an inert gas containing oxygen is passed, ζ. Β. Air, at a temperature of about 300 to 600 ⁰ C through the mass. The time required for activation varies depending on the temperature used and the oxygen content of the flowing gas. For example, for 125 g of silica gel (Merck, No. 7733) with a chromium content of 1% using air with a flow rate of 100 l / hour at 500 "C, it is about 30 minutes. After activation, the metals are present as" surface compounds " For example, the oxidation number for 1% chromium on the support listed in Table I with the protected designation "Marlex" is about 5.7 and for 1% chromium on the support also mentioned in Table I. with the protected designation "MS 969" about 5.9. In addition, the activated compositions have characteristic colors depending on the transition metal component they contain.

After activation with oxygen, the masses are reduced at elevated temperatures with Treated gases. Examples of suitable gases are given in Table III below, with chromium-containing Crowds were reduced. The reduction with hydrogen and especially with can be particularly effective Carry out carbon monoxide. For this reason and because of their easy accessibility, these gases are preferred. If desired, the reducing gases can also be diluted with inert gases. the The masses are reduced like activation in the gas flow. In general it is for the reduction at least a temperature of 200 ° C and a time of a few minutes required. The optimal one Reduction temperature depends on both the type of reducing gas and the one used Mass from. From table II it can be seen which reduction temperatures for the reduction of masses, which contain various transition metal components, with carbon monoxide are advantageous. In table IM are the favorable reduction temperatures for various reducing gases in the example! chromium-containing Masses explained. The optimal conditions for other cases can easily be determined by preliminary experiments determine.

It should be noted, however, that the choice of the reducing gas and the reduction conditions such as temperature and duration of treatment are decisive for the effectiveness of the finished masses Meaning is. The presence of water makes the reduction reaction more difficult. Hence are reducing gases such as hydrogen or saturated hydrocarbons that are under during the reduction Formation of water can react less effectively than carbon monoxide, which becomes harmless Carbon dioxide is oxidized. Furthermore, when heated, as is known, also from OH groups des The carrier is split off with the formation of oxide bridges. The reduction is therefore at as possible to carry out mild conditions. Ultimately, an irreversible »healing« takes place at higher temperatures the surface under (also irreversible) incorporation of the reduction products into deeper layers of the Carrier material. The metal atoms bonded in this way are not in spite of a possibly low oxidation number more effective according to the invention. For this reason, masses are made of a heat-resistant oxide Carrier with a metal-containing component, such as those known from BE-PS 6 55 115, door that method according to the invention useless.

The processes involved in treatment with reducing Gases take place, although not all details are known, but it is certain that the used transition metals, which after activation with oxygen predominantly in higher oxidation states are present, with oxidation of the reducing agent essentially in lower oxidation states pass over.

For example, by reducing activated chromium-containing masses with carbon monoxide during 10 minutes at 230 C and 1 atmosphere products

obtained in which the oxidation number of chromium is 2.0 + 0.1. However, this low oxidation number, which is essential for the usability of the mass in the process according to the invention, is not achieved if the work is carried out at a higher temperature and / or with too long a reduction time, since the above-mentioned disruptive processes then occur. Is is known that can be activated chromium-containing compounds, such as those used for the ethylene polymerization or dehydrogenation of hydrocarbons, at 500 ⁰ C with hydrogen or carbon monoxide reducing and that the reduction products, similar such as an aqueous Cr (II) solution , are sensitive to oxygen, but in the products known to date, more than 50% of the chromium is in the form of chromium (III), which is not sensitive to oxygen.

In all cases there is a visual discoloration of the masses watch during the reduction. In Tables II and III, such color changes are for various Examples listed. Since the color change when the masses transition from activated to reduced form appears very sharp and clearly recognizable, it can be used to advantage to To determine the progression and, above all, the end of the reduction.

While it is well known that some compounds of transition metals with a low oxidation number, also in solution or in pure form with oxygen react, for example compounds of Cr (II) or Ti (III). For the extraordinary described below The effectiveness of the compositions according to the invention, however, is the presence of these oxidation stages in Surface connections are crucial. Compounds of metals can also be used in this form whose lower valence levels are otherwise not sensitive to oxygen, for example rhenium or nickel. The activation described above is necessary for the formation of surface connections necessary precondition under oxidizing conditions. If, on the other hand, the carrier is doped from the outset with corresponding metal compounds with a lower oxidation number, there are no for the purposes of the invention which can be used to obtain products.

The masses obtained after the treatment described are ready for use and can in the Process according to the invention are used. Shouldn't the gas used for the reduction itself later are subjected to the method according to the invention, it may be useful before implementation of the process according to the invention, reducing gas retained on the compositions according to the invention by desorption with inert gas, e.g. B. to remove nitrogen or the gas to be cleaned. In which The method according to the invention has a surprising property of the compositions prepared in this way Made use, namely that they are able to bind the above-mentioned admixtures.

It has already been stated that by impregnating a silica-alumina carrier with Chromsäurclösung, drying, activation with 4 hours of heating ⁿ in a stream of air at 550 C and Istündipcs heating with Kohlcnmonoxyd at 100 mm to 250 C, a composition is obtained that the Polymerization of ethylene catalyzed at low temperatures. The same effect is achieved if, instead of the treatment with carbon monoxide under the conditions given above, a 1 hour treatment with 2.5 moles of ethylene per gram atom of chromium is carried out at 150 ° C Effect not achieved.Compositions of this kind have been described only for the polymerization of ethylene.

It is therefore very surprising that a large number of homogeneously dissolved admixtures, as mentioned above can be removed from gases or liquids in that the gases or liquids mi the masses described above are brought into contact. In doing so, the media will be the ones to be removed Removed admixtures and taken up by the mass. In which way this recording is made is not known, but it is assumed that the admixtures are essentially due to the active Component of the mass is chemically bound. The masses are therefore referred to below as chemisorption called medium. Of the various Bcimengun conditions, oxygen is most strongly bound. It was found that oxygen is other additions already bound to the compositions according to the invention able to suppress. In addition, since the measures known for the removal of oxygen are irr Compared to measures that are known for the removal of other admixtures, the practical The method according to the invention is preferred for removal before meeting needs the least Oxygen applied.

The absorption capacity of the chemisorption center for oxygen decreases with increasing load, bi it is eventually exhausted. In all cases this point in time can also be determined visually. So watch in the case of chromium-containing chemisorbents, which, as stated above, after treatment with a reducing gas have a blue color, that the oxygen uptake of a sharp color change is accompanied by brownish yellow. When the original color has disappeared throughout the mass, that is Depleted capacity for oxygen. Such color changes also occur in other admixtures as shown in Table IV. As will be explained below, the used Chcmisorp Simply regenerate the agent and can then be used again.

According to the invention, oxygen can be obtained from gaseous or liquid media within a very wide range Temperature range. The lower limit of this range is essentially only through practical reasons determined. For example, with chromium-containing compounds, they were even left to cool on cooling The liquid air temperature obtained useful results as seen in Table II. After upper the applicable temperature range extends bi; to the limit of the thermal stability of the at dei Activation resulting higher oxides under activation conditions. Within this wide area the most appropriate temperature can be selected in each individual case. In many cases it is special: It is advantageous to work at room temperature, as no heat supply or cooling is required.

The capacity of the masses is determined by the redeixcriti occurring during the chemisorption. Sc it was found, for example, that at Vcrwendunj chromium-containing masses 0.15 to 0.85 mol O ^ pr < Gram-atom of Cr are added.

The method according to the invention can also be used

use numerous gases and liquids. Below various gases are listed, from which oxygen with chromium-containing masses at 20 "C (except Ethylene) can be removed. When cleaning ethylene, the range is between - 45 ° C and + 200 ° C not suitable, as the formation of polyethylene occurs here.

Noble gases

hydrogen

nitrogen

Carbon monoxide

Carbon dioxide

Hydrogen sulfide *)

Ammonia*)

Shark hydrogen *)

Ethylene *)

Saturated hydrocarbons

*) Activation required after consumption.

The term gases, as used herein, also includes vapors of normally understood liquid substances. To liquid media from which oxygen is removed according to the invention can include z. B. saturated hydrocarbons, aromatic hydrocarbons and ethers.

With the method according to the invention, oxygen can be removed practically quantitatively. So became for example after passing air at room temperature through a chromium-containing chemisorbent obtained practically oxygen-free gas, the oxygen content of which is below the mass spectrometric detectable value of 1 part per million. In the German patent specification 9 65 634 it is indicated that with the catalysts described there can also remove oxygen very effectively. To the For comparison, a mixture of oxygen and nitrogen was passed over such a catalyst, and then the prepurified nitrogen was replaced by a chromium-containing mass according to the invention let flow. Considerable amounts of oxygen were still able to be extracted from the pre-cleaned nitrogen removed.

For the regeneration of the chemisorbents, whose capacity is exhausted by loading with oxygen, the same treatment with reducing gases is used as above for the preparation of the masses used according to the invention has been described. The regeneration becomes the original The ability to take up oxygen is restored. You can also take advantage of the above Make use of the color change described above in order to determine the location of the regenerating treatment. If the media from which the oxygen contained therein is to be removed are reducing gases, as used for the reducing treatment described above in the manufacture of the chemisorbents are used, the process can advantageously be carried out continuously without regeneration of the chemisorbent is required. In this case the gas will be at the same Temperatures such as those above for treatment with reducing gases during manufacture of the Chemisorbents were specified, brought into contact. It is not known whether among these Conditions first a chemisorption of the oxygen by the mass and then a regeneration by the reducing gas, or whether both processes take place at the same time. It was However, found that the effectiveness of the mass is retained, so that this embodiment as Combustion of the reducing gas with the oxygen can be viewed as the mass acts as a catalyst, as it were. Under certain circumstances, the combustion product can be used without any detriment in the treated gas remain. However, it can easily be removed by known means if necessary. The process according to the invention can also be carried out continuously with such gases possible not or only for the reducing treatment for the preparation of the chemisorbents are not very suitable, but due to oxygen in the presence of the chemisorbents used according to the invention be oxidized under such conditions.

Many of the chemisorplants described have a long life so that they are repeated loaded and then regenerated again by simple reduction. After a long time However, it may be appropriate to use a reactivation with oxygen or an oxygen-containing one Inert gas at elevated temperature under the same conditions as those used above for manufacture of the masses were described to perform, for example to remove deposits that are after Prolonged use can form on the chemisorbents and reduce their effectiveness. To Reactivation with oxygen must of course still undergo the treatment described above before use be carried out with reducing gases. How often is the chemisorbent loaded and then can be regenerated by simple reduction before reactivation with oxygen is necessary, also depends on the type of gas used for the reduction, as can be seen from Table III.

Tabel II 3 4th 5 6th 7th 8th 1 2 activation Color of Red. With Color of Minim. Temp. comment Metal! Doping mil with air activated form CO at red. shape f. response aq. Solved by with Ch 500 ° C whitish yellow 350 ° C blue <20 ° C, quickly reversible Ti TiCb 500 ° C White 320 ° C black >; 120 ° C reversible V (ΝΗφνΟ « 500 ° C yellow-brown 250 ° C blue") 2-190 ° C, reversible Cr CrOa quickly 500 ° C yellow-brown 250 ° C blue') δ-190 ° C, reversible Cr (NOa) ₃ quickly 500 ° C White 350 ° C gray-brown > 120 ° C reversible Mon (NH «) 3MoO4

110

! ■ onset / lint! 2 3 4th 5 . with
at H 7th 8th 1 Doping mil
aq. I.sg. from activation
with air Color of
activated form Red
CO nnnn Color of
red. shape Minim. Temp,
f. response
with ().' comment metal Mn (NO3) 2
Re2Or
Fe (NOa) ₃
Ni (NOj) 2 500 ° C
500 ° C
500 ° C
500 ° C black-brown
White
Red
black-brown 350
300
250
200 gray-green
black-brown
black
gray-green ai5o ° c
> 120 ° C
> 120 ° C ^J ) reversible
reversible
reversible
reversible Mn
re
Fe
Ni

After desorption of CO by N2 (previously violet-blue). At 2U slow reaction with color change to brown. ^J i Slow reaction at 20 °.

Table III

Reduction of chromium-doped masses
with different gases

gas

Red temp.

Color of

reduced

Dimensions

effectiveness
to remove O2

I. Co ') 250 ° violet blue outstanding H H22) 350 ° blue green very good Methane ³ ) 300 ° blue green Well Propane ³ ) 400 ° greyish green moderate t Ethylene ³ ) 200 ° blue green satisfactory v'r- Town gas ³ ) 350 ° blue green satisfactory

¹ I Fully reducible after reaction with oxygen.

² I Can only be reduced 2–3 times, then activation required.

>) Activation required after consumption.

The method according to the invention can, for example, be used to purify gases or liquids from added oxygen can be used. Such cleaning is necessary, for example, when the presence of oxygen has a disruptive effect due to its chemical reactivity. Included the oxygen content often has to be extremely low. However, the cleaning effort increases increasing requirements with regard to the oxygen concentration. Since the invention Chemisorbents used are very easily accessible, but oxygen is extraordinary able to effectively remove, it is particularly advantageous to use the method according to the invention on gases or to use liquids, the oxygen content of which is relatively low, but practical Does not meet needs. Such post-cleaning is necessary, for example, for noble gases that technically produced and in large quantities, for example for arc welding with shielding gas, as an inert gas filling for incandescent lamps, as a carrier of the passage of current and the generation of radiation in low pressure or Ultra-high pressure discharge lamps, as ignition gas in mercury and sodium vapor lamps or for electronic ones Switching elements, e.g. B. Rectifiers can be used.

Nitrogen produced on a large scale by liquefying air must also be freed of its oxygen content for numerous purposes. Nitrogen is the most commonly used protection or Inert gas. This is the case in nylon production, for example oxygen-free nitrogen in large quantities for the conversion of adipic acid with hexamethylenediamine and required as a protective gas during spinning. Further examples are the tempering of stainless steel by annealing in an oxygen-free stream of nitrogen and the use of nitrogen as a carrier gas for the Trace elements introduced into the germanium crystals during the manufacture of diodes and transistors as well as in the manufacture of the purest semiconductors. It will be apparent to those skilled in the art that the Application of the measures according to the invention also offers advantages in many other cases, e.g. B. to Removal of small amounts of dissolved oxygen from solvents used in the manufacture of sensitive ones Products are used or to obtain a gas in pure form from mixtures of the desired gas with oxygen alone or together with other admixtures. In the following Table IV gives examples of such substances other than oxygen, those of the invention used reduced masses are bound by chemisorption. The experiments were made with chromium-containing Masses carried out.

Table IV Reactive Color change from Responsive to comment gas Temp. blue after O2 at 20 ° 20 ° violet very good with 02/500 ° CO enableable 20 ° yellow-brown - the same SO2 20 ° black-brown moderate the same H2S 20 ° dark brown moderate the same NO 20 ° violet very good the same NH3 20 ° green - the same CI2 20 ° beige satisfactory the same HCl 20 ° green satisfactory the same Benzene vapor

The method according to the invention can also be used for the analytical detection of oxygen and for a semi-quantitative determination of very small amounts of oxygen, similar to the type of known test tube (Gas detector from Draeger, Lübeck, see e.g. H. Römpp, Chemielexikon, 6th edition, 1966, Stuttgart, Page 1599).

Devices suitable for carrying out the method according to the invention are shown in FIGS and 3 shown.

Fig. 1 shows an arrangement for removing oxygen or other admixed gases from technical nitrogen and other gases. The gas to be cleaned flows out of the reservoir z. B. a steel bottle 1 with technical nitrogen via a connecting line to the columnar container 2 which is filled with the chemical sorbent. This connecting line is provided with a pressure relief valve 3 in order to prevent excessive loading of the arrangement in the event of a sudden increase in pressure. The line can have devices (not shown) for regulating and measuring the gas flow. The oxygen-free gas flows from the container 2 via a connecting line into the container 4, which is used to remove moisture from CC ^ traces with a desiccant 5, e.g. B. Mg (ClO ₄ ^, and a CO2 sorbent 6, z. B. soda asbestos, is filled. Dry, oxygen-free gas flows out of the container 4. The arrangement shown in FIG Chemisorbent in container 2 is loaded with oxygen or other admixtures until its capacity is exhausted, then regenerated and, if necessary, reactivated and can then be used again.

The arrangement shown in Figure 2 is suitable for the continuous conversion of oxygen with reducing gas, as well as for the treatment of fresher or spent chemisorbents with oxygen or reducing gases. That at point 7 Incoming gas flows via a connecting line into the container 8, which is with the chemisorbent is filled. The container 8 is of a heating device 9, for. B. a tube furnace surrounded. By regulating the Heating device 9 is set to the desired temperature and with the help of the temperature measuring device 10 monitors. The flowing medium reaches the container 11, where it is collected and in the case of Vapors condensed or can be removed for further use.

F i g. 3 shows an arrangement suitable for removing oxygen from liquids. it consists of a receptacle for the liquid, e.g. B. a dropping funnel 12, which is connected to the column 13, in which the Chemisorbent is located, is connected. To the column 13 closes a collecting vessel 14 for the bottom treated liquid. The dropping funnel 12 is filled with the liquid from which oxygen is to be removed z. B. diethyl ether filled. Between the dropping funnel 12 and the column 13 filled with chemisorbent there is a shut-off device, e.g. B. a tap with which the inflow of the liquid into the column 13 can be regulated. The liquid flows downwards through the filling under the influence of gravity and reaches the collecting vessel via a connecting piece, which is also provided with a shut-off device 14. To increase the flow rate, overpressure can be applied to the dropping funnel 12 or underpressure can be applied to the column 13 or the collecting vessel 14.

With these arrangements, the gas throughput can expediently be between 5 and 250 l / h. For Liquids speeds of up to 4 l / h come into consideration.

ilier / u I sheet Zeidinuniien

Claims (3)

Patent claims: 1. A method for removing homogeneously dissolved oxygen, nitrogen oxide, hydrogen halide, halogen, hydrogen sulfide, sulfur dioxide, sulfur trioxide, ammonia and / or carbon monoxide from gases, saturated or aromatic hydrocarbons or ethers using a mass consisting of a carrier material with a or consists of several applied metal components and which has been treated at elevated temperature with oxygen and / or reducing gases, characterized in that the admixtures are removed by chemisorption by ^{activating the gases or liquids with a molecular oxygen at 300 to 600 0} C and then with a reducing gas at a temperature between 200 ⁰ C to below the particular activation temperature treated mass from an active iron-, nickel-, rhenium-, preferably titanium-, manganese-, vanadium, molybdenum and / or chromium-containing component on a heat-resistant oxidic carrier it can be brought into contact with a large surface. 2. The method according to claim 1, characterized in that the impregnated air-dry carrier contains the metal component in an amount of 1 to 5% by weight, based on the metal content. 3. The method according to claim 1 or 2 for removing oxygen, characterized in that that a mass with a chromium-containing component is used wildly.